At present, polycarbonate is one of thermoplastics that have been widely used in many industries such as vehicle industry, appliance industry, and electronic industry because of their unique characteristics such as transparency, strength, and impact resistance. However, polycarbonate has some disadvantages which limit its application, including chemical resistance and low heat resistance. Therefore, there have been attempts to improve the polycarbonate properties in order to overcome said problems by mixing and/or synthesizing polycarbonate with other polymers that can tolerate high heat and chemicals such as polyetherimide.
U.S. Pat. No. 4,548,997 disclosed polymer blends between polycarbonate and polyetherimide. Said polymer showed better heat resistance comparing to polycarbonate. However, it was found that the polymer blends according to said patent gave lower impact resistance which might be resulted from the incompatibility of polycarbonate and polyetherimide. This could be seen from the two glass transition temperatures of said polymer blends, in which one belonged to polycarbonate and the other belonged to polyetherimide. The compatibility of both polymers is a limitation for the development of heat and mechanical properties.
U.S. Pat. No. 4,393,190 disclosed the preparation method of poly(carbonate-etherimide) from diimide having hydroxyl terminal group by the reaction with polyhydric phenol and phosgene. The obtained copolymer according to said patent had the glass transition temperature close to polycarbonate. This can be presumed that the hydroxyl terminal group of diimide had lower reactivity comparing to polyhydric phenol, leading to the obstacle of diimide in its reaction. Thus, the obtained copolymer yielded the low etherimide content in its structure, showing the limitation of said reaction. However, said patent did not disclose the heat or mechanical properties of the obtained polymer. Moreover, the use of phosgene as a reactant is a concerned issue due to its high toxicity, especially to the respiratory system.
U.S. Pat. No. 4,611,048 disclosed the preparation of short chain polyetherimide having hydroxyl terminal group. The said polyetherimide could be reacted with polyhydric phenol and phosgene to give poly(carbonate-etherimide) block copolymer by the interfacial polymerization disclosed in U.S. Pat. No. 4,657,977. Said method gave the copolymer with a random block. This would limit its use and be difficult to control the block distribution. Moreover, the use of phosgene the use of phosgene as a reactant is a concerned issue due to its high toxicity, especially to the respiratory system.
U.S. Pat. No. 4,757,150 disclosed the preparation method of poly(carbonate-etherimide). The said method comprised the preparation of bischloroformate from the reaction of polyetherimide bisphenol and phosgene. Then, said bischloroformate was further reacted in order to prepare cyclic heterocarbonate and poly(carbonate-etherimide) respectively. However, said method still used phosgene as its precursor of carbonate. Moreover, the copolymer prepared by the method according to said patent had 2 glass transition temperatures which were 148° C. and 210° C., indicating the separation of polycarbonate and polyetherimide into 2 phases.
U.S. Pat. No. 6,096,853 disclosed the preparation of poly(carbonate-etherimide) having higher heat resistance comparing to normal polycarbonate. The said method comprised the preparation of diimide having hydroxyl terminal group from the reaction of dianhydride and aminophenol. Then, said diimide was reacted with phosgene or other carbonate precursors by melt polymerization or interfacial polymerization to obtain poly(carbonate-etherimide), in which the glass transition temperature was in a range from about 160 to 175° C. However, said melt polymerization has to be performed at the high temperature, which caused high energy consumption and might be problematic in an industrial scale production.
Until present, there have been many attempts to develop other carbonate compounds for preparing poly(carbonate-etherimide) through melt polymerization to avoid the use of phosgene which is highly toxic. For example, U.S. Pat. No. 7,230,066 disclosed the preparation of carbonate-etherimide block copolymer using bis-methyl salicyl carbonate as a precursor of carbonate and reacted with polyhydric phenol and polyetherimide having hydroxyl terminal group via melt polymerization at a high temperature in a range of from 230 to 300° C. Due to melt polymerization, the reaction was performed at a high temperature, resulting in high energy consumption. Moreover, bis-methyl salicyl carbonate is an expensive chemical comparing to other carbonate precursors.
U.S. Pat. No. 4,713,439 disclosed the preparation of poly(carbonate-etherimide) without the use of phosgene. Diaminodiphenyl carbonate was used as a carbonate precursor and was reacted with dianiline via cyclization reaction at a temperature about 300° C. This leads to high energy consumption and might be problematic in an industrial scale production.
U.S. Pat. No. 5,756,643 disclosed the preparation of polyimide copolymer comprising a hard segment of polyimide and a soft segment of aliphatic polycarbonate or a mixture of aliphatic polycarbonate and aliphatic polyester. Said method was consisted of the mixing of dianhydride and aliphatic polycarbonate diol to form an ester bond and yield an oligomer having anhydride terminal group. Then, the obtained oligomer was reacted with diamine at high temperature in a range of from about 220 to 300° C. to obtain a polyimide copolymer. The obtained copolymer possessed imide, carbonate, ester, and carboxylic groups in the structure. The ester functional group in the structure might reduce the heat and chemical resistance in the copolymer.
From the reasons mentioned above, this invention aims to develop new method to prepare poly(carbonate-etherimide) in which said method does not contain a highly toxic phosgene, can be performed easily, and can be operated at not high temperature, in which the obtained poly(carbonate-etherimide) has suitable properties and structure for further applications that require strength and high heat resistance especially as the compatibilizer for polymer blend of polycarbonate and polyetherimide to improve its compatibility.